A study by Oxford University has established that the efficacy of the Pfizer Inc. (NYSE: PFE) vaccine against the delta variant of the coronavirus drops after three months.

Pfizer’s vaccine efficacy was after three months 

The UK government ran the study whose results are yet to be peer-reviewed and evaluated data collected through a large-scale survey of thousands of households tested for the virus at the start of November. This was the time when the Delta variant was dominant in the country. 

The study authors indicated that the AstraZeneca vaccine’s efficacy was much lower compared to Pfizer’s in cases where the Delta variant was dominant. Still, the Pfizer vaccine’s efficacy dropped with time. The researchers estimated that the two vaccines are effective against the Delta variant 4-5 months after individuals have received the second dose. 

The authors stated, “The dynamics of protection varied over time from second vaccination, and by vaccine type, with initially larger effectiveness with [Pfizer’s vaccine] than [AstraZeneca’s], which then become more similar by ~4-5 months due to more rapid waning of effectiveness with [Pfizer’s], particularly against infections with [high viral loads] or symptoms.”

Even vaccinated individuals show the same viral levels as unvaccinated. 

The study showed that the Pfizer vaccine’s efficacy against the burdensome strains was 92%, 14 days, after vaccination and 78% after three months. According to the study, people with the Delta variant that had received either vaccine had similar peak virus levels as those infected and had not received the vaccine.  As a result, this has potential ramifications on transmission risk in the future. 

One of the study authors, Dr. Koen Pouwels, said, “Whilst vaccinations reduce the chance of getting Covid-19, they do not eliminate it. More importantly, our data shows the potential for vaccinated individuals to still pass Covid-19 onto others, and the importance of testing and self-isolation to reduce transmission risk.”